Unfortunately, custom work such as doing the work or providing tutorials how to do something is not really part of theme support…I know, not what you wanted to hear. I have done some custom work for others but it’s considered billable time. To do what you want is not a simple copy and paste some code, the structure of the menu would have to change, such as the containers. My best recommendation is to hire a designer or developer (if you are not able to do this) to provide them with details of what you are wanting done.
The only other option is to put your flags in a widget in a widget position somewhere, such as the right or left columns, or anywhere that does not require custom coding.